The Quest Diagnostics Drug Testing Index (DTI)™ examines illicit drug use by the U.S. workforce based on an analysis of the results of more than 9.5 million urine, 900,000 oral fluid, and 200,000 hair laboratory-based drug tests performed nationally by the company for employers in 2015.

DTI data from 2015 shows the positivity rate for 9.5 million urine drug tests in the U.S. workforce increased to four percent. The last year that the positivity rate for urine drug tests in the combined U.S. workforce was at or above four percent was 2005, when it reached 4.1 percent.

The DTI found the rate of amphetamine, marijuana, and heroin detection in drug tests in the U.S. workforce increased annually over the past five years in urine testing, with amphetamine increasing 44 percent, marijuana increasing 26 percent, and heroin increasing 146 percent since 2011.

In addition, the rising positivity rate for post-accident urine drug tests increased 6.2 percent in 2015 when compared to 2014 and 30 percent since 2011. Post-accident positivity for drug tests of safety-sensitive workers rose 22 percent during a five-year time period (2.8% in 2015 versus 2.3% in 2011).